Your first example shows a couple of confusions.
1) "Los hombres de Doyle le tienen miedo" - Doyle's guys are scared of him. Here "le" is not used in the meaning "him". So why simply not to say like this: "Los hombres de Doyle tiene miedo de él".
It seems here you are trying to translate literally from English, and also mixing up two alternative syntaxes for the idiomatic phrase tener miedo. You'll understand it better with simpler examples using some imaginary characters Alice and Bob:
- Alice tiene miedo de Bob.
- Alice le tiene miedo a Bob.
Both of these mean "Alice fears Bob; Alice is afraid/scared of Bob". In #1 we use a complement headed by de. In #2 we use an indirect object, which (as usual) is preceded by a. In the latter example we also have to use le, even though it looks redundant, because that's a rule (Alice tiene miedo a Bob is ungrammatical). If we replace Bob by a pronoun, we have:
- Alice tiene miedo de él.
- Alice le tiene miedo a él.
In this version of #2, adding a él is emphatic. If the context is such that it's already clear who is being referred to (él), the last part becomes truly redundant and you could leave it out:
- Alice le tiene miedo.
We would only add a él in this case if we want to emphasize that Alice is afraid of "him" and not of somebody else.
As for the second example:
2) Same here, but in plural: "¿No les temes?" - "And are you not scared of them?"
Here we have the verb temer, not the phrase tener miedo. Temer is a somewhat complicated verb because it can be used as transitive or intransitive but with an indirect object. The latter is more common, especially when speaking of fear of people, and that's what's happening here. That's why it's ¿No les temes? and not ¿No los temes?. It works the same as the second pattern that we've seen for tener miedo.
The emphatic version would add a redundant pronoun:
¿No les temes a ellos?
If we wanted to name the people you fear explicitly, we'd have to do it as above:
¿No les temes a los hombres de Doyle?
I hope this clarifies your doubts a bit. If not, just say so in the comments.